INIA researchers and others have posited that stress and alcohol exposure trigger allostatic processes which injure limbic and hypothalamic stress pathways and set the stage for increased drinking. This theory is supported by epidemiological findings in the US population that number of life stressors is positively correlated with amount of alcohol consumption and that these effects are strongest in persons with an early onset of alcohol use. Recent studies suggest important modifying effects of the serotonin transporter promoter polymorphism and stress in predicting total alcohol intake, age of onset of drinking, and duration of drinking. Genetic variation in the corticotropin-releasing hormone (CRH) receptor 1 also has been associated with stress-induced heavy alcohol consumption in animals and human adolescents; the role of CRH has been a major focus of INIA. We hypothesize that, in the human laboratory, a social stress procedure will increase alcohol motivated responding and alcohol consumption, and that this relationship will be modified by age of drinking onset and the genes under investigation. To test our hypotheses, non-treatment seeking, heavy alcohol drinkers with and without an alcohol use disorder will be admitted to the clinical research unit for alcohol detoxification. Four days after the start of abstinence, subjects will undergo in random order, the Trier Social Stress Test (TSST) or a time-matched neutral condition; Cortisol will be measured during these procedures. Immediately after the TSST or neutral condition, access to alcohol will be provided using an operant self-administration paradigm in which the response demands progressively increase with each alcohol drink that is earned; earned alcohol is delivered at the conclusion of the session. We also will study subjects using an alcohol sensitivity procedure that establishes a dose-effect function for alcohol on subjective, physiological and behavioral measures within a single session. Study findings will have scientific and clinical importance in establishing potential mechanisms for genetic and environmental influences on the relationship between stress and alcohol in heavy drinkers.